Computing and communication networks typically include devices, such as routers, switches or gateways, which transfer or switch data, such as packets, from one or more sources to one or more destinations. A packet is a structure that encapsulates data for transmission through a network based on control information that is stored in a header portion of the packet.
A network switch, in particular, may include a networking device that connects network segments and computing devices. Output ports for network switches are frequently connected using twisted-pair copper wires to form the physical layer for packet transmission. The Ethernet protocol is typically used to implement the data link layer over the physical layer. The Ethernet protocol can, however, also provide a data link layer over other physical layers, such as optical fiber or twisted pair cable. One type of implementation of a port designed to support Ethernet over twisted pair cable also includes a way to supply power to the connected device over the same cable. This type of port is called Power-over-Ethernet (PoE) port, and is defined by IEEE standard 802.3.